1. Technical Field
The present invention relates to a display apparatus and a display method thereof, in particular, to a mobile display apparatus using an optical modulator and a display method thereof.
2. Description of the Related Art
An optical signal processing has advantages such as fastness, a capability for parallel processing, and a capability of processing a large volume of information, compared to an existing digital information processing which cannot deal with large volume of data and cannot perform a real time processing. Besides, there have been studies on a design of a binary phase filter, an optical logic gate, an optical amplifier, an optical element, and an optical modulator. using space optical modulation theory. Among them, the optical modulator is applied to an optical memory, an optical display device, a printer, an optical interconnection, and a hologram, and a light beam scanning device using the optical modulator is under development.
Such a light beam scanning device in a laser printer, an LED printer, an electric photo copier, a word processor and a projector, scans a light beam and spots a photosensitive medium with the light beam, thereby generating an image.
As a projection TV has been introduced, the light beam scanning device is also employed as a beam projector.
FIG. 1A is a schematic view of a display device using an optical modulator and a polygon mirror according to a prior art. In FIG. 1A are illustrated a light source 110, a control part 120, a lens 130, a polygon mirror 140, and a screen 150. Here, an optical modulator is dispensable in a mobile projector, but descriptions below will concentrate on a mobile projector using an optical modulator.
The light source 110 generates a laser beam, which is later reflected and diffracted by the optical modulator. Here, the light source 110 generates the laser beams simultaneously in a vertical direction, and such laser beams create a two-dimensional image by the rotating polygon mirror 140. The light source 110 may be composed of a laser or a laser diode, and the control part 120 controls the light source 110 to turn on/off, whereupon a laser beam is generated.
The control part 120 also controls a driving of the polygon mirror 140.
The lens 130 collects the laser beams emitted from the light source 110 toward a rotation axis of the polygon mirror 140.
The control part 120 controls the polygon mirror 140 to be turned on/off, and the polygon mirror 140 rotates constantly at a predetermined angular speed. Such a polygon mirror 140 has a polygonal shape, each side of which reflects an incident beam.
The polygon mirror 140 has a bidirectionally rotatable motor (not shown in the accompanying drawings), and rotates due to the motor to reflect an incident beam projected through the lens 130 toward the screen 150.
The configuration of such a display apparatus will be set forth in detail with FIG. 1B. FIG. 1B is a block diagram of a mobile display apparatus control part according to a prior art. Referring to FIG. 1B, R, G, and B image signals are inputted from a mobile display apparatus 160 to a mobile display apparatus control part 170. Here, an image signal input part 173 transfers image signals, comprising R, G, and B digital data and timing signals, transferred from the mobile display apparatus 160 to an image correcting part 171. Then, the image correcting part 171 corrects the image signals according to a deviation between elements or color characteristics of the image signals. Here, the image correcting part 171 is connected to an external memory 180, and reads an initial set value therefrom to perform a correcting process using correction logic.
An image data synchronization signal output part 175 makes an image signal pivot from a raster scan direction to a vertical direction, and transfers synchronization signals per frame, pixel synchronization signals, and vertical line output timing signals to a panel driver 183.
The panel driver 183 converts digital image data to analog signals, and drives an optical modulator panel 186 in synchronization with the vertical line output timing signal. Also, the panel driver 183 matches an image gradient to an output voltage level by referring to an analog voltage range decided in an upper electrode voltage range regulating part 172.
The optical modulator panel 186 is mechanically deformed by a voltage difference between an upper electrode and a lower electrode (a voltage is applied by a lower electrode voltage control part 174), and modulates the amount of diffraction of a light emitted from a light source 192.
A scanner output control part 176 outputs a position control signal of a scanning device 196 to a scanner driver 194, in synchronization with the vertical line output timing signal. A light source output control unit 177 generates and then transfers a light source control signal to a light source driver 190 driving a light source 192, so that R, G and B light sources sequentially operate in synchronization with the image synchronization signal. A memory 180 stores therein correction values (classified by pixel and color) with respect to the image correcting part 171, a range of upper electrode voltages, an initial set value of a lower electrode voltage, a scanner profile, and a light source output set value.
Here, in the case of using the optical modulator and the polygon mirror 140, the mobile projector needs to synchronize the polygon mirror 140 with the image signals in order to project certain beams onto the screen 150. In other words, in order to reflect a corresponding image to the screen 150 through an effective area of the polygon mirror 140, the image synchronization signal and a rotation of the polygon mirror need to be controlled to project a laser beam corresponding to the image signal to the effective area.